1. Technical Field
Embodiments of the present disclosure relate to inverter circuits, and particularly to an inverter circuit with a protection circuit.
2. Description of Related Art
Discharge lamps, such as Cold Cathode Fluorescent Lamps (CCFLs) and External Electrode Fluorescent Lamps (EEFLs), have been broadly used as light sources in liquid crystal display (LCD) systems. The discharge lamps are often driven by high voltage. To protect the discharge lamps and ensure proper operation, a detection circuit detects voltage applied to the discharge lamps and current flowing through the discharge lamps.
FIG. 5 shows a commonly used inverter circuit for powering a light source module 14. The inverter circuit comprises an input signal circuit 10, a power stage circuit 11, a transformer circuit 12, a voltage detection circuit 13, a feedback circuit 15 and a pulse-width modulation (PWM) control circuit 16. The PWM control circuit 16 comprises a PWM controller and driving circuit 161 and a latch signal generator 162.
In a normal status, the PWM controller and driving circuit 161 controls output of the power stage circuit 11 according to a feedback signal to adjust current flowing through the light source module 14. In an abnormal status of the inverter circuit, the voltage applied to or current flowing through the light source module 14 exceeds individual predetermined threshold, and the latch signal generator 162 generates a latch signal according to the output of the voltage detection circuit 13 or the feedback circuit 15. In addition, the PWM controller and driving circuit 161 outputs a switch signal according to the latch signal to the power stage circuit 11, to cut power to the light source module 14.
Frequently, the PWM controller and driving circuit 161 and the latch signal generator 162 are integrated into the PWM control circuit 16 normally a chip. Thus, in different inverter circuits, a detection circuit is designed based on actual selected PWM control circuit 16 to provide protection. In addition, parameters of the PWM control circuit 16 are fixed and cannot be modified.